Field of the Invention
The present invention relates to a substance for reversibly absorbing and desorbing hydrogen, and its isotope, particularly a reversible hydrogen and its isotope absorbing-desorbing substance which is easy in hydrogenation and large in hydrogen absorbing and desorbing rate, more particularly, to a reversible hydrogen and it's isotope absorbing-desorbing substance with a comparatively high hydride composition and showing a lower equilibrium pressure than an atmospheric pressure at a temperature of less than 300.degree. C., and also for getting the other gasses.
Hitherto, as a substance showing a lower hydrogen dissociation pressure than an atmospheric pressure at a temperature of less than 300.degree. C. among hydrogen getting materials, Ti, Zr, Hf and the like have been known. However, these metals are covered with strong oxides and nitrides, so that in order to obtain a hydrogen-gettable clean active surface, there is required a pretreatment for once sublimation by a sputtering method or heat-treatment at a high temperature of 700.degree.-1,000.degree. C.
Recently, there has been tried improvement of a pretreatment such as activation by adding 2nd, 3rd, 4th, . . . elements to these metals to form an alloy, and controlling the hydrogen dissociation pressure characteristic by adding the 2nd, 3rd and 4th elements, or enlarging a reversible absorbing-desorbing rate of hydrogen.
However, among these metals, Zr-Al, Zr-Ni alloys, for instance, should be treated with heat-treatment or activation at a high temperature such as 450.degree.-750.degree. C., and even if Zr-V alloy can reversibly absorb and desorb hydrogen without an initial activation treatment, if the alloy is exposed to hydrogen gas of about 0.5 kg/cm.sup.2 when a temperature of initially absorbing hydrogen is ZrV.sub.0.15, a temperature is high such as about 230.degree. C. and an absorbing rate at that time is slow. Further, in Zr-V alloy, although no powder treatment is required, there is a viscosity to some extent and comparative solid, so that it is difficult to adjust this alloy to a desired size, that is, cutting and crushing.
Further, there has also been known intermetallic compound Zr-V-O and the like stabilized by oxygen, but there are such disadvantages that an activation treatment is required and regulation of a sample grain size is difficult because of hard alloy. There have been known to control a hydrogen dissociation pressure, to regulate a sample grain size and to improve characteristics to gas other than hydrogen gas by adding the 4th and 5th elements to an alloy stabilized with oxygen and forming an intermetallic compound such as Zr-Ti-V-Fe-O, but with the increase of kinds of addition elements, it has been difficult to regulate the substance to a desired composition.